Low voltage generator



June 11, 1935. H, G. FISCHER ET Al. 2,004,17 51 LOW VOLTAGE GENERATORFiled March 2s, 1951 5 sheewsheet 1 @l A .l/Q10 .frm/mr r/me 6mm/wc gti.fix/aa Jig 14 Ir-g '13 'Y /Msnmvf 6u.

June ll, 19.35. V H. G. FISCHER rAL LOW VOLTAGE GENERATOR Filed March25, 1931 5 Sheets- Sheet 2 RE.. Sula.

June 11, 1935.. H. G. FlscHR Erm. 2,004,751

LOW VOLTAGE GENERATOR y Filed March 23, 1931 5 Sheets-Sheet 5 June 11,1935. H, G FlscHER Er AL 2,004,751

LOW VOLTAGE GENERATOR Filed March 23, 1951 I -5 sheets-sheet 4' gf/ ff Aa June ll, 1935.l

Filed March 23, 1931 G. FISCHER El' AL OW VOLTAGE GENERATOR 5Sheets-Sheet 5 J/ 4.9 Jg JZ x K/ 1: EC. GEN. :lil Home n.6. GEN. j

Patented June 11, 1935 LOW VOLTAGE GENERATOR.

Herman G. Fischer. Peter P. Musket, and Donald sigma E. Richardson.Chicago, Ill.,

tou. G.

Fischer Company, Chicago, Ill., a corporation of Illinois ApplicationMatch 23, 1931, Scrll'l No. 524,530

'9 Claim.. (Cl. lil-07) This invention relates in general tomulti-current generators and while it has more particular reference tomulti-current generators for generating electric current of varying waveform for the use in electro-physiotherapy, it will be readily apparentthat the invention is capable of employing an apparatus for other andmore general use.

A principal object of the present invention is the provision of anapparatus of simple construction and certain operation for producing thevarious currents desired in electro-physiotherapy, the particularcurrent being provided by the apparatus through simple external controlsso constructed and operating that the usual physician can employ theapparatus with certainty and with lminimum of directions.

Another important object of the invention is the provision of anapparatus of the character described, the parts of which will be ofsimple, sturdy construction, and unlikely to require frequent repair,replacement, or internal readjustment in use.

The invention contemplates the provision of a simple low voltage,multi-wave apparatus, for use in electro-physiotherapy, which willproduce, at the option of the operator and through the manipulation ofsimple controls, currents designated as straight galvanic, pulsatinggalvanic, rapid alternating. galvanic surge, pulsating gal- -vanicsurge, rapid alternating surge, slow sinusoidal, pulsating slowsinusoidal, rapid alternating in surges, and various modifications ofthese current wave forms to provide dwells and periods of rest.

Numerous other objects and advantages of the invention will be apparentas it is better understood from the following description, which, takenin connection with the accompanying drawings, discloses a preferredembodiment thereof.

Referring to the drawings:

Figures l to 15 inclusive are diagrammatic views illiltrtin graphicallythe wave forms of various current adapted for generation by theapparatus in which the present invention is embodied;

Fig. 18 is a front elevation of an apparatus embodying our presentinvention, the internal parts being shown in section;

Fig. 17 is an enlarged fragmentary elevation of the commutator and brushmechanism employed in the apparatus; l

Fig. 18 is an end view of the brush head and associated parts;

Fig. 19 is a transverse longitudinal section through the collectorrings;

Fig. 20 is a section taken substantially on the line Il--ll of Fig. 19;

Fig. 2l is a front elevation of the commutator;

Fig. 22 is a side view thereof and Fig. 23 is a wiring diagram of theseveral cir- 5 cuits of the apparatus.

The apparatus shown on the drawings, and which constitutes theembodiment of the invention at present preferred, comprises generally,an outer housing Ii. in which is mounted a motor generator unit 32having a shaft 33 adapted through suitable friction gearing, generallyindicated at 34, to drive a shaft l5 upon which is mounted a set ofcollector rings 36 and which is provided at its ends with a brush head31. The brush head 31 carries brushes generally -in dicatcd at 38, andwhich` will be presently more fully described. These brushes in theirmovement engage and move over a commutator 39 to which direct current issupplied by the gen- 20 erator unit 22. The control of the apparatus andthe selection of the various wave forms to be produced is accomplishedthrough two switches 4I and 42 which in cooperation with the circuitwiring, illustrated in Fig. 23, determine the 25 current characteristicof the apparatus at each treatment. A main switch 43 is arranged in thecircuit as are also volt and ammcters 44 and 45. A rheostat, generallyindicated at 4B, is provided and controlled by an external knob 41 and apolarity reversing switch 48 is or may be provided if desired.

A motor generator unit. as may be seen from Fig. 23, comprises anelectric motor 49. a direct current generator il, and an alternatingcur- 35 rent generator or current modulator 52. The motor 49 and thegenerators 5i and 52 are mounted upon a common shaft 5I which is rotatedby the motor. This shaft is provided with a worm 84 which engages a wormgear 55 (Fig. i8) fixed for rotation with the friction disc 34. Afriction wheel mounted to slide lengthwise of the shaft 35 may be movedby the hand nut il to impart rotation at desired speed to the shaft 35.

Referring more particularly to Figs. 17 to 22, it will be noted that theshaft l5 is provided at its lefthand end with a brush head 58 secured at59 upon the end of the shaft. This brush head in the instant embodimentof the invention is provided with three sockets, identified by referencecharacters Il, 82 and 63, in which are mounted three brushes 64, and 66.The shaft ll is provided with four collector rings, indicatedrespectively at 61, 68,69 and 1|. These collector rings are mountedbetween collars 12 and 13 and are insulated from each other and from thesurrounding structure at 14.

Wires 15 and 16 lead respectively from brushes 65 and 66 to collectorrings 68 and 61. A wire 11 leads from brush 64 to collector ring 69.,Viewing Fig. 20, it will be noted that collector ring 1| is dividedinto segments 18 and 19 insulated from each other at 8|. The segment 18is electrically connected by a wire 82 with the brush 64 so that thisbrush is electrically connected to both the collector ring 69 and 1|.Suitable xed brushes 83 are provided for continuous engagement with thecollector rings as they rotate, and these brushes deliver and receivethe current from the stationary portion of the circuit wiring to bepresently described.

A commutator or resistance element shown in Figs. 17, 21 and 22, ismounted for engagement by the brushes 64, 65 and 66 as they rotate withthe shaft 35. This commutator is built up of a plurality of intermediateparallel bars 84 of relatively narrow sides edges. The bars 84 areinsulated from each other at 85. Wider blocks or bars 86 are arranged atthe ends or top and bottom of the commutator. The bars 84 and blocks 86together with the interposed insulation 85 is tightly clamped into asingle compact unit by bolts 81, with the presented edges or faces ofthese parts in a single plane for engagement with the brushes. 'I'heblocks 86 and the bars 84 are electrically connected to interposedresistance coils, which will now be described.

Each bar 84 is extended alternately at its end, as may be seen bycomparing Figs. 17 and 21, to provide lugs 88 and 89, and on adjacentbars the position of the lugs is reversed, this arrangement providingroom for wires 9| and 92 to be connected to the extended ends or lugs ofthe bars by soldering or in other suitable manner.

A resistance coil is arranged in the connection between each twosuccessively arranged or adjacent bars 84. These coils, generallyindicated at 93, are wound about a carrier 94 arranged back or to theleft of the unit formed of the bars 84 and blocks 86. An inletterminal95 is connected by a wire 96 with the bottommost bar 84, viewing Fig.21. This bar is in electrical contact with thevbottom block 86. 'I'hewiring is such that current passing through the commutator and in at theterminal 95 flows first in and through the bottom bar 84 and block 86,thence serially through the successively arranged bars 84 and theinterposed resistance coils 93 to the top bar 84 and top block 86. Thelast mentioned parts are connected by a wire 91 with a second terminal98.

Wire connects one side ofthe direct current generator with a wire |02connected in turn to terminal 95. A wire |03 connects terminal 98 with awire |04 which in turn is connected to the movable element of therheostat 46, this rheostat being in turn connected by wire |06 with thedirect current generator.

The control and selection of the various circuits is accomplished bymanipulation of the switches 4| and 42. The switch 4|, as indicated inFig. 23, is a triple switch having three xed contacts F adapted to beconnected by the usual arcuately swinging arm with contacts A, B, C, ADand E, a set of which is appropriately arranged for and about eachcontact F. The switch 42 is likewise a triple switch, having xedcontacts 4 adapted for connection with the usual switch arm withsimilarly arranged sets of arcuately positioned contacts I, 2 and 3.

After thus describing the major mechanical parts and devices in theapparatus in which the invention is at present embodied, a fullunderstanding of it, it is believed, can be easiest accomplished. by adescription of the electrical circuits established to produce thecurrent form illustrated in Figs. 1 to 15, and in describing thesecurrents letter and numeral designation is employed in accordance withthe switch positions of the switches 4| and 42, the letter designationsreferring to the contacts A, B, C, D and E of switch 4 I, and thenumeral designations referring to the contacts 2 and 3 of switch 42. Itmay be mentioned in this connection that like letter and numeraldesignation of position is indicated upon index plates |01 and |08arranged upon the front of the casing 3| to guide the physician or otheruser in the selection of his circuit. It will be understood that theswitch 4| is a three arm switch, each arm of which pivots about aterminal F and into contact with the terminals or contacts A, B, C, Dand E, lthe three arms moving together at each switch manipulation. Theswitch 42 similarly is comprised of three arms respectively movableabout terminals or contacts 4 and simultaneously into engagement with'the three contacts 2 and 3. Each arm in each switch is insulated fromlother arms and completes its own independent portion of the circuit tobe formed.

Circuit A-|, which is the circuit established when contact F isconnected with contact A, and contact 4 with the contact providesthestraight galvanic current, Fig. 1 of the drawings. The circuit forthis current is established as follows: Wire |0| from D. C. generator 5|leads to contact C, which in turn is connected to contact B to contactA. A wire |09 leads from com-. panion contact F to a wave filter (whichis or may be provided to reduce or prevent rippling of the various waveforms of the currents provided in the operation of the apparatus). Thiswavek filter is not thought to need particular. description since itsconstruction provides no part of the present invention. It may bementioned, however, that it comprises reactance units ||2 and ||3 andcondensers ||4 and ||5 suitably wired together. From the wave lterv awire ||6 leads to contact points 2 and of the righthand unit of switch42. From point the circuit continues through contact 4 to wire I1 (inwhich is or may be arranged the ammeter 45). Wire ||1 connects Withterminal ||8 at the pole changing switch 4 8 and through the polechanging switch with one or the other of load terminals ||9 to which theelectrodes delivering the current to the patient is connected. From thepole changing switch the circuit continues through terminal 2| tocontact 4 over wire |22. From contact to contact 3 through wire |23 tointermediate terminal F of switch 4| to contact A of this switch andwires |24, |04 to rheostat 46 and thence to wire |06 to generator 5|.

A volt-meter 44 may be put across this circuit between contact F of theintermediate unit of switch 4| and contact of righthand unit of switch42 by wires |25 and |26. A wire |21 leads from contact of lefthand unitof switch 42 to wire |28 to the middle of the condensers ||4 and ||5onlter In tracing this circuit, it will be observed that the currentpasses without alteration through the load terminals ||9 and is onlyaffected in its y is - and its wiring is as follows: wire IOI, wire |02to the commutator and to the point B of lefthand unit of switch 4 I. Onecircuit is completed from the commutator by wire |03 through rheostat 46and wire |06 back to D. C. generator 5I. The other circuit continuesfrom B to F, wire |09 to filter, wire ||5 to contact I of righthand unitof switch 42, contact 4 to wire |I1, contact ||6, contact |2|, wire |22,contacts 4 to I of lefthand unit of switch 42, wire |23 to intermediatecontact F of switch 4|, contact B, wire |29 to collector ring 91 andfrom this ring to brush 65 in engaging with the commutator. The circuitcontinues through terminal 93, wire |03, rheostat 46, and wire |06 AtoD. C. current generator. This circuit includes like connection to wire|23, |21 and wire |26 to intermediate portion oi.' condensers ||4 andI|5 on the filter III and the volt-meter 44 is included in the circuitas earlier described.

Direct current ilows through the circuits and the brush 65 in movingoverthe commutator causes the current to surge irom zero to a maximum andback to zero again, as may be observed in Fig. 4.

Current C-I (Fig. '7) provides a galvanic dwell with the surge and aquarter of the cycle as a rest period for the patient. In this circuit,the current flows from generator 5| as before to the commutator and tocontact C oi' the leithand unit of switch 4|. From this contact tocontact F, wire |09 to lter and thence as described in connection withthe earlier circuits to wire`||6, contacts 2, I and 4, wire II1 toterminals ||3 and |2I at the pole chan-ging switch. From here thecurrent flows to wire |22, contacts 4, I and 3 of lefthand unit ofswitch 42, and thence by wire |23 to intermediate contact F oi switch4|. From here the circuit continues through wire I3| leading fromcontact C to colflector ring 69, and from collector ring 56 to brush 66and from brush through commutator, wire |03, rheostat 46, and wire |06to D. C. generator 5|.

It will be noted that brush 66 has travelled over the end blocks of thecommutator and that when the patients current reaches a maximum, as

occurs when the brush engages the top block (viewing Fig. 23) a dwell isprovided which gives the wave form shown in Fig. '1 of the drawings. Atthe opposite diameter oi! the movement, the brush 66 is in contact withthe bottom block and through the bottom block directly with the wire|03, so that`no current flows through the load portion of the circuitoris received by the patient. This gives a rest dwell of zero current. Asbefore, the volt-meter 44 is arranged across the circuit and connectionis made with the middle of the filter.

Current D-I oi slow sinusoidal form, as shown in Fig. 10, is producedthrough the circuit to be now described: wire I0| to wire |02 toterminal of commutator; from commutator the circuit is completed throughterminal 98, wire |03, wire |04, rheostat 46, wire |06`to generator.Brush 55 and collector ring 61 are connected by wire |29 to contacts Band D oiintermediate switch unit 4|. Contact F of this unit is connectedby wire |23 to contacts 3 and of lefthand unit of switch 42 and thecircuit continues through contact 4, wire |22, terminals |2| and ||9,wire |I1 to contacts 4, I and 2 of righthand switch unit 42, wire II6,alter III, wire |09 to contact F and D of lefthand unit of switch 4|,wire |32 connects this contact D with a collector ring 69 in turnconnected with brush 64. It will be noted that the two brushes 64 and 60travel continuously over the commutator bars 34 and impart modulatedcurrent of the true sign form shown in Fig. 10.

Current E-I (Fig. 10), which is a galvanic surge giving a two-thirdsrest period, is provided through wiring as follows: The commutator issupplied with current as described in the immediately preceding circuitsand, as before described, is returned to the generator. Brush 65 andcoilector ring 61 are connected by wire |29, the contacts B, D and E otthe intermediate unit of switch 4I. Wire |23 connects contact F withcontacts 3 and I ot lefthand unit oi switch 42. 'Ihe circuit continuesthrough wire |22, contacts |2| ||6,'wire |I1 to contact 4 of righthandunit of switch 42; thence by contacts I and 2, wire ||6, iilter II|,wire |09, contact F of lefthand unit of switch 4 I, and thence bycontact E, wire |33 to the active segment o! collector ring 1| and tobrush 64 at the commutator. By reason of the idle period oi thecollector ring 1| a two-thirds period of rest is provided in theresulting galvanic circuit.

Current A-2 is the pulsating galvanic current shown in Fig. 2. Thecircuit comprises wire IOI through contacts C, B and A of lefthand unitot switch 4I, wire |09, illter I|I, wire II6, contacts 2 and 4 ofrighthand unit of switch 42, wire I|1, terminals ||9 and |2|, wire I 22to contacts 4 and 2 of lefthand unit of switch 42, wire |34 and wire |35to A. C. generator 52. The current thence flows by wire |36 to contactsand 3 of lefthand unit of switch 42, wire |23 to contacts F and A ofintermediate unit of switch 4I, and then back to generator through wire|24, wire |04, movable contact |05, rheostat 46 and wire |06. In the A.C. generator, which is preferably an induction generator, an A. C.current is generated by induction and upon this a D. C. current issuperimposed to give the wa've form shown in Fig. 2 of the drawings. Theneld of the A. C. generator is excited by the circuit to be nowdescribed: wire |0| to contacts C, B, A, contact F, wire I 09 tocontacts 4, 2, 3 of intermediate unit of switch 42, wire |31 togenerator 52, wire |36 to contacts I and 3 of lefthand unit of switch42, wire |23 to contact F of intermediate unit of switch 4|, contact Aof this unit, wire |24, wire |04', rheostat 45, and wire |06 to D. C.generator. At the A. C. generator, wire |36 is provided to connect bothto the I A galvanic to pulsating galvanic. The circuit comprises wireIOI to contacts C and B of lefthand unit of switch 4|, wire |09 ofcontact F to illter wire ||6 to contacts 2 and 4 of righthand unit ofswitch 42, wire I|1 to terminals ||6 and |2|, wire |22 to contacts 4 and2 of lefthand unit of switch 42. The circuit then continues throughwires |34 and |35 to A. C. generator, from the A. C. generator wires |36and |21 connect contacts I and 3 o! lefthand unit of switch 42. Wire |23leads from contact 3 to contact F of intermediate unit of switch 4|which is connected to contact B in turn connected by wire |29 tocollector ring 61 of brush 65 in engagement with the commutator. Thecircuit is completed through terminal 96, wire |03, wire |04, rheostat46 and wire generator is excited as just above described in connectionwith current A--2.

Current C-2 is the pulsating galvanic dwell surge with the one-quarterrest period shown in Fig. 8. This circuit comprises wire to the point Cof the lefthand unit of switch 4|, Wire |09 to filter wire ||6 tocontacts 2 and 4 of 'the righthand unit of switch 42, wire ||1,terminals ||8, |2|, wire |22 to contacts 4 and 2 of the lefthand unit ofswitch 42, wire |34, wire |35 to A. C. generator 52, wire |36 to contactpoints I and 3 of the lefthand unit of switch 42, wire |23 to contacts Fand C of the intermediate unit of switch 4|, wire |3| to collector ring68 and brush 66 in engagement with the commutator. From the commutator,the circuit is completed through terminal 98, wire 03, movable contact|05, rheostat 46 and wire |06 to D. C. generator 5|. rent and itscircuit and the current and circuit of the galvanic dwell surge of Fig.7. The field of the A. C. generator is excited as just above describedin connection with current A-2.

Current D-2, which is the pulsating slow sinusoidal current of Fig. 11is produced as follows: wire |0| leads to wire |02 and the terminal 95of the commutator and an energizing circuit is completed from terminal98, wire |03, wire |04, rheostat 46 and wire |06 back to D. C. generator5|. Brush 65 in contact with this generator and its collector ring 61are connectedby wire |29 to contacts B, D of intermediate unit of switch4|. Wire |23 connects contact F of this unit with contacts 3 and oflefthand unit of switch 42 and wires |21 and |36 connect to A. C.generator 52. From the A. C. generator wire |35 and wire |34 lead tocontacts 2 and 4 of leithand unit of switch 42 and the circuit continuesto terminals |.2| and ||8, wire ||1, contacts 4 and 2 of right-y handunit of switch 42, and wire ||6 to lter From the filter wire |09 leadsto contacts F and D of lefthand unit of switch 4| and from contact Dwire |32 leads to collector ring 69 of brush 64. The eld of the A. C.generator is excited as just above described in connection with currentA-2.

Current E-2, which is the pulsating galvanic surge with the two-thirdsrest period, and which is illustrated in Fig. 14, is produced asfollows: The current, as earlier described, is caused to flow from theD. C. generator through the commutator and back to the generator. Thecircuit for supplying this current to the terminals ||8 and |2| is asfollows: brush 65 andcollector ring 61 are connected by wire |29 tocontacts B, D and E of intermediate unit of switch 4|. Contact F of thisunit is connected by wire |23 to contacts 3 and of lefthand unit ofswitch 42. From the contact of this switch wires |21 and |36 lead to A.C. generator 52. From this generator, wire |35 and wire 34 lead tocontacts 2 and 4 of lefthand unit of switch 42. The circuit continues insequence as follows:Y wire 22,

-terminals |2| and ||8, wire ||1, contacts 4 and 2 of righthand unit ofswitch 42, wire |l6, filter wire |09, contacts F and E of lefthand unitof switch 4|, wire |33, active segment of col-A lector ring 1| and brush64. The eld of the A. C. generator is excited as just above described inconnection with current A Z.

Current A-3 is therapid alternating current illustrated in Fig. 3 of thedrawings. The circuit for .it in sequence is as follows: Wire I 0I,contacts C, B and A of lefthand unit of switch 4|,

Comparison is suggested between this cur' contact F, wire |09 tocontacts 4 and 3 of intermediate unit of switch 42, wire L31 to A. O.generator 52, wire |36, contacts and 3 of letthand yunit of switch42wire |23 to contacts F and A of intermediate unit of switch, wire |24,wire |04, rheostat 46 and wire 06 to D. C. generator 5|. 'I'he circuitthus completed is a. generating or field circuit for the A. C.generator. From the A. C. generator a delivery circuit is formed asfollows: wire |35, wire |30, contacts 3 and 4 of righthand unit ofswitch 42, wire ||1, terminals ||8 and |2|, Wire |22, terminals 4, 3 andof llefthand switch unit of switch 42, wire |21 and wire |36 back to A.C. generator.

Current B-4, which is the rapid alternating current in surges, isillustrated in Fig. 6, and is produced by creating a field or deliverycircuit in the A. C. generator. Wire |0| leads to contacts C and B oflefthand unit of switch 4|, wire |09 leads to contact 4 of theintermediate unit of switch 42, and wire |31 connects contact 3 of thisunit to the eld of the A. C. generator 52. From this eld, wires |36 and|21 lead to contacts and 3 of lefthand switch unit of switch 42, andwire |23 leads to contact F of the intermediate unit of switch 4|. Thecircuit continues: Contact B, wire |29, collector ring 61, brush 66 tothe commutator and from the commutator by wires |03, |04 to rheostat 46and wire |00 to the D. C. generator. The delivery circuit is the same asthat already described for circuit A3.

Current C--3 is the rapid alternation in dwell surges with the quarterrest period as shown in Fig. 9. A eld circuit for the A. C. generator isprovided as follows: Wire 0| to contacts C,

and F of lefthand unit of switch 4| wire |00 to contacts 3 and 4 ofintermediate unit of switch 42, wire 31 to A. C. generator, wire |30land wire |21, contacts and 3 of lefthand unit of switch 42, wire |23 tocontacts F and C of intermediate unit of switch 4|, wire |3| tocollector ring 68 and brush 66, to terminal 90, wire |03, wire |04,rheostat 46 and-wire |06 to D. C. generator. The delivery circuit is thesame as that already described in connection with the immediatelypreceding circuit, series 3.

Current D-3 is the current of Fig. 12 producing rapid alternations insurges (see Fig. 6) Here the held circuit is energized as follows: Wire|0| from the A. C. generator 5| connects by wire |02 with terminal 95 ofthe commutator. The current iiows through the resistances of thecommutator to terminal 98 and back through wire |03, wire |04, rheostat46 to the D. C. generator 5|. Brush 05 and collector ring 61 areconnected by wire |29 to contacts B, D, and F. The circuit continues insequence as follows: wire |23, contacts 3 and of lefthand unit of switch42, wire |21, wire |36, the field of A. C. generator 52, wire |31,contacts 3 and 4 of intermediate unit of switch 42, wire |09 to'contacts F and D of lefthand unit of switch 4|, wire |32 to collectorring 69 and brush 64. 'I'he delivery circuit is that already describedin connection with the circuit of the 3 series now being described.

circuit r'f-s, which is the rapid alternating circuit with thetwo-thirds rest period, shown in Fig.

15, is produced as follows: The current is caused field of A. C.generator 52. Wire |31 leads to contacts 3, l of intermediate unit ofswitch l2, and

wire |09 connects these contacts with contacts F.

lleading respectively fromtaps |43 and I at the commutator andconnecting to terminals F and E of the righthand unit of switch 4i.

In all of the foregoing circuits. the volt meter 44 is connected asdescribed in explanation of circuits A-I and B-i and similar wiring isprovided to tap into the center of the filter, as earlier described.

It is thought that this invention and many of its attendant advantageswill be understood from the foregoing description, and it is apparentthat various changes may be made in the form, construction andarrangement of the parts without departing from the spirit and scope ofthe invention or sacrificing all of its material advantages, the formhereinbefore described being merely a preferred embodiment thereof.

l. An apparatus for generating currents of wave form for use inelectro-physiotherapy and for other uses, comprising in combination, aseries of contact bars arranged with their edges in a single plane,resistances interposed between and connected to said contact bars inelectrical series, terminals at the ends of the series of bars, a directcurrent generator connected with said terminals, a brush having relativemovement over said contact bars for variously receiving currenttherefrom, a source of alternating current, a pair of load terminals andselectively operable means for making, varying and breaking connectionsbetween said load terminals and said brush, and also between said loadterminals and said source of alternating current to superimpose analternating current upon the direct current passing between said loadterminals.

2. An apparatus for generating current of wave form for use inelectro-physiotherapy and for other uses, comprising in combination adirect current generator, an alternating current generator, a rotarycommutator consisting of a plurality of axially alined rings, aplurality of brushes severally connected with said rings, said brushesbeing movable jointly with said rings, resistance elements over whichsaid brushes are maintained in sliding engagement, said resistanceelements being connected with the direct current generator, selectivelyoperable means for altering the connection between said resistanceelements and said generator, and selectively operable means forestablishing connection between said alternating current generator andsaid brushes `to superimpose the alternating current of said alternatingcurrent generator upon the direct current, the selectively operablemeans interposed between the alternating current generator and thebrushes being connected with load terminals for leading oil the modifiedcurrent.

3. An apparatus for generating current of wave form for use inelectro-physiotherapy and for other uses, comprising in combination, aseries of contact bars arranged with their edges in a single plane,resistances interposed between and connected to said contact bars inelectrical series. terminals at the two ends of the series of bars. adirect current generator connected with said terminals, a brushmechanism having relative movement on said contact bars for receivingcurrent therefrom, said brush mechanism including a plurality ofbrushes, a pair of load terminals. a source of alternatingcurrent, andmeans for variously connecting'rrsaid brushes and said alternatingcurrent with said load terminals to superimpose an alternating currentupon the direct current passing between said load terminals.

4. An apparatus for generating current of wave form for use inelectro-physiotherapy and for other uses, comprising in combination, aseries of contact bars arranged with their edges in a single plane,resistances interposed between and connected to said contact bars inelectrical series, terminals at the two ends of the series of bars, adirect current generator connected with said terminals, a brushmechanism having relative movement on said contact bara for receivingcurrent therefrom, said brush mechanism comprising three brushes, loadterminals, a source of alternating current, and means for selectivelyconnecting said brushes in pairs and said source of alternating currentto said load terminals to superimpose an alternating current upon thedirect current passing between said load terminals.

5. An apparatus for generating current of wave form for use inelectro-physiotherapy and for other uses, comprising in combination, aseries of contact bars arranged with their edges in a single plane,resistances interposed between and connected to said contact bars inelectrical series,l terminals at the two ends. of the series of bars, adirect current generator connected with said terminals, a brushmechanism having relative movement on said contact bars for receivingcurrent therefrom, said brush mechanism comprising three brushes, asource of alternating current, load terminals, and means for selectivelyconnecting said brushes singly and in pairs to said load terminals andalso for selectively connecting said source of alternating current tosaid load terminals to superimpose an alternating current upon thedirect current passing between said load terminals.

6. An apparatus for generating current of wave form for use inelectro-physiotherapy and for other uses, including an aggregateconsisting of an alined motor, direct current generator and alternatingcurrent generator, a commutator. having a plurality of axially alinedelectrically insulated rings, said commutator being rotated by saidmotor, a plurality of brushes severally conductively connected with saidrings and also rotated by said motor, a plurality of .alined resistancebars over which said brushes travel while successively engagingdifferent bars, the resistance elements being connected with said directcurrent generator, a plurality of switches interposed between saiddirect current generator, and some of said brushes, and adapted to varythe electric connection between said commutator rings and saidgenerator, and another plurality of switches interposed between saidalternating current generator and said first named switches additionallyto vary the relation of said brushes to said resistances and tosuperimpose an alternating current of selectively variable form upon thedirect current of selectively variable form.

